Viewstate verification failed

Question

I know why I'm getting this error and know how to fix it, but need to ask a few questions I couldn't find out by searching the web.

Our application is in a Web Farm and was looking into changing the validationKey from AutoGenerate,IsolateApps to a specific manually generated key value.

However, as a sample (I checked my local machine, not the actual server machine.config file as I don't have access to it). All I see in my local machine.config is a setting like below:

<section name="machineKey" type="System.Web.Configuration.MachineKeySection, System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" 
allowDefinition="MachineToApplication"/>

In order to possibly update it, I was expecting to see something like below:

<machineKey validationKey="AutoGenerate,IsolateApps"  
            decryptionKey="AutoGenerate,IsolateApps" 
            validation="SHA1" decryption="Auto" />

How come I'm not seeing that on my local machine. Or, if it is different on a server (like above), if I change the setting to a manual key, will it affect other applications that run on the Web Farm? If so, is there a specific time to change it?

If I opt out of that, and choose to update the web.config file instead for that application, all I need to do is to just simply update that one specific web.config file where the application resides. Correct?

Answer 1

Yes, just update the Web.config for the specific application, and make sure that Web.config is deployed under the application folder to all machines in the farm. This won't affect any other applications running on those machines.

If you need assistance generating a <machineKey> element, see http://support.microsoft.com/kb/2915218 (Cause 1 and Appendix A).